Many methods for analyzing specific components in fluid samples have hitherto been developed and these methods may be divided broadly into two types of a reaction system wherein reactions take place in a solution and a reaction system wherein reactions take place in a solid place carrier. A broad range including the method which does not use an instrument at all and is called a `manual` method up to an automatic analyzing instrument is known as an analytical reaction in a solution system (hereinafter referred to as `wet chemistry`). Especially in the field of clinical chemistry, its progress is remarkable and various kinds of quantitative analysis instruments for clinical chemistry have recently been introduced to clinical diagnostic loboratories of hospitals.
However, aforesaid methods have various disadvantages because reactions are basically made in the form of an aqueous solution in aforesaid methods. Namely, they cause an increase in energy consumption because they require much water, especially refined pure water or distilled water in the course of analysis. Further, various kinds of automatic analyzing instruments themselves are extremely expensive and require much skillfulness in the operation thereof and they not only require immense time and labor but also inevitably cause an environmental pollution with waste liquids therefrom. In contrast to aforesaid methods, analytical methods employing analytical reactions in solid phase system (hereinafter referred to as `dry chemistry`) are broadly used and they are performed in the form of a filter paper or the like containing reagent.
Aforesaid filter paper is prepared in a way wherein a water-absorbing fibrous carrier such as a filter paper is contained with reagent solution and then is dried as shown in U.S. Pat. No. 3,050,373 or U.S. Pat. No. 3,061,523, for example. This is generally called an analytical test paper or simply a test piece and fluid sample is dropped on a test piece or a test piece is dipped in a fluid sample and a color change or an optical density change on the test piece is checked visually or measured with a reflecting densitometer, thus a density level of specific component in the fluid sample is determined.
These test pieces are useful because they are handy and provide a immediate result but due to their structure, they can not lie outside the region of a semi-quantitative analysis or a qualitative analysis.
In contrast with the conventional analyzing method like the foregoing, on the other hand, there is known a multi-layer analytical element which employs a handy dry chemistry and yet provides a high quantitativeness. For example, multi-layer analytical elements are disclosed in Japanese Patent Examined Publication No. 21677/1978, Japanese Patent Publication Open to Public Inspection Nos. 164,356/1980, 125,847/1982, 197,466/1982 and 90167/1983.
According to the elements described in aforesaid documents, all of the reagents used for analytical reactions are contained in a sheet of analytical element and blood serum or complete blood in a certain amount is dropped on aforesaid element which is then kept at a certain temperature for a certain period of time and then the reflecting density on the element is measured from the support side, thus it is possible to determine the substance concentration from aforesaid reflecting density.
Aforesaid method is far excellent in the accuracy of analysis compared with the conventional one of a test paper type and owns an efficiency higher than that of wet chemistry without preparing reagent in advance.
In the analytical element employing such dry chemistry, however, it is very difficult to cause the analytical element to contain enzyme that catalyzes a reaction system necessary for measuring an object to be tested, keeping the activity of aforesaid enzyme.